New log, log2, exp, exp2 and pow implementations (#992)

Author: MaxGraey

NOTICE

@@ -35,6 +35,31 @@ the following terms:
   Copyright 2015 WebAssembly Community Group participants
   Apache License, Version 2.0 (see LICENSE file)
 
+* Arm Optimized Routines: https://github.com/ARM-software/optimized-routines
+
+  ----------------------------------------------------------------------
+  MIT License
+
+  Copyright (c) 1999-2019, Arm Limited.
+
+  Permission is hereby granted, free of charge, to any person obtaining a copy
+  of this software and associated documentation files (the "Software"), to deal
+  in the Software without restriction, including without limitation the rights
+  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+  copies of the Software, and to permit persons to whom the Software is
+  furnished to do so, subject to the following conditions:
+
+  The above copyright notice and this permission notice shall be included in all
+  copies or substantial portions of the Software.
+
+  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+  SOFTWARE.
+
 * musl: http://www.musl-libc.org
 
   musl as a whole is licensed under the following standard MIT license:

std/assembly/index.d.ts

@@ -1677,6 +1677,8 @@ interface INativeMath<T> extends IMath<T> {
   rem(x: T, y: T): T;
   /** Returns sin and cos simultaneously for same angle. Results stored to `sincos_s32/64` and `sincos_c32/64` globals */
   sincos(x: T): void;
+  /** Returns 2 raised to the given power x. Equivalent to 2 ** x. */
+  exp2(x: T): T;
 }
 
 /** Double precision math imported from JavaScript. */